Mechanical bridge plug capable of being drilled and fished

Abstract

The invention relates to the technical field of oil production engineering, and particularly discloses a drillable mechanical bridge plug which comprises a connecting pipe, an upper cone, an elastic locking piece, a slip assembly, a lower cone, a rubber barrel and a shaft end fixing piece, the upper cone is slidably connected to one end of the connecting pipe, and a butt joint is arranged at one end of the upper cone and extends out of the connecting pipe; the elastic locking piece is connected to the connecting pipe and used for limiting the upper cone, the other end of the upper cone is connected with one end of the slip assembly, the slip assembly is slidably connected to the connecting pipe, the other end of the slip assembly is connected with one end of the lower cone, the lower cone is slidably connected to the connecting pipe, the other end of the lower cone abuts against one end of the glue barrel, and the glue barrel is slidably connected to the connecting pipe. The shaft end fixing piece is connected to the other end of the connecting pipe and abuts against the other end of the glue barrel. The mechanical bridge plug capable of being drilled and fished is high in reliability, convenient to drill and mill and convenient to take out later.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production engineering, and particularly to a drillable fishing mechanical bridge plug. Background Art

[0002] During the oilfield exploration and development process, since there are often multiple formations in oil and gas wells, and the formation properties vary greatly, in order to better understand the different characteristics of each formation, separate layer well testing is essential. Moreover, in stimulation measures such as fracturing and acidizing, separate layer operations are often carried out. In various string operations, the use of bridge plugs is necessary. A bridge plug is a widely used device for separating layers in oil and gas wells at home and abroad. Its function is the same as that of a cement plug, playing an isolation role in the separate layer oil production process of oil and gas wells. Developing and exploiting unconventional oil and gas resources must rely on reservoir stimulation technologies such as hydraulic fracturing and acid fracturing. Among them, the technology of using bridge plugs for multi-layer and multi-stage fracturing is a very common technology, and downhole tools are the key to the development of these reservoir stimulation technologies.

[0003] Currently, the bridge plugs commonly used in oilfields have disadvantages such as corrosion and rusting when they need to be removed later, being unable to be fished out, or being unable to be processed after getting stuck, difficult to mill, long milling time (the more plugged intervals, the longer the required milling time), difficult backflow, and low reliability.

[0004] Chinese Patent Publication No. CN2690585Y provides a dual-purpose squeeze-injectable drillable bridge plug. It is a dual-purpose squeeze-injectable drillable bridge plug designed for water shutoff in oil well formations, which can continuously perform sand washing and well flushing and squeeze-injection of cement slurry operations on the same tubing string. Its feature is that a sliding sleeve is designed on the central hole of the bridge plug. When sand washing and well flushing, the inner hole of the sliding sleeve is open, and the flushing operation can be directly carried out. When squeezing the plugging agent, a steel ball is dropped to seal the inner hole of the sliding sleeve, so that after the bridge plug is set, the sliding sleeve is burst, and the liquid outlet hole is exposed for squeezing cement slurry.

[0005] Chinese Patent Publication No. CN2876318Y provides a retrievable and drillable bridge plug above, which includes a mandrel, a central tube, a bi-directional anchoring device, a sealing assembly, an upper and lower double locking device, and an unlocking device. The feature of this utility model is on-site setting, fishing, and releasing. In the case where fishing and releasing do not fail, it can be released by drilling and grinding. It is applicable to the string operation measures such as plugging bottom water, selective layer acid fracturing, and up-return well testing in oil and gas wells during oilfield exploration and development.

[0006] Chinese Patent Publication No. CN2833099Y provides a high-pressure drillable bridge plug. In the annular cavity where the upper cone is threadedly connected to the central pipe, there is a secondary piston locking pressure locking block. The secondary piston is locked to the main piston by shear pins. The main piston is threadedly locked to the upper cone, and the upper cone, slips and the core shaft are threadedly locked. The slips are fixed by slip shear pins. The upper end of the tension rod is movably hinged to the central pipe and the lower end is threadedly connected to the core shaft. The lower cone is hung on the shoulder of the core shaft and fixed by lower cone shear pins. The upper and lower ends of the rubber barrel below press against the protective cover, and the lower pressing ring below is threadedly connected to the core shaft. A locking spring is installed in the inner groove on the inner side of the upper cone to lock the core shaft. The outer surface of the slips is an annular tooth and the inner surface is a thread. This bridge plug is suitable for selective layer fracturing of oil wells, plugging bottom water and making a cement plug for an artificial bottom hole.

[0007] Therefore, the present invention provides a drillable mechanical bridge plug to overcome the defects of the prior art. Summary of the Invention

[0008] The present invention provides a drillable mechanical bridge plug, which solves the problems of the bridge plugs commonly used in current oil fields in the above-mentioned background technology, such as corrosion and rusting when they need to be removed later, inability to fish or process after getting stuck, difficult to drill and mill, long drilling and milling time (the more plugging intervals, the longer the required drilling and milling time), difficult to flow back, and low reliability.

[0009] To achieve the above objectives, the present invention is realized through the following technical solutions:

[0010] A drillable mechanical bridge plug includes a connecting pipe, an upper cone, an elastic locking member, a slip assembly, a lower cone, a rubber barrel and an end fixing member. The upper cone is slidably connected to one end of the connecting pipe, and a docking head is provided at one end of the upper cone and extends outside the connecting pipe. The elastic locking member is connected to the connecting pipe for limiting the upper cone. The other end of the upper cone is connected to one end of the slip assembly. The slip assembly is slidably connected to the connecting pipe, and the other end is connected to one end of the lower cone. The lower cone is slidably connected to the connecting pipe, and the other end of the lower cone abuts against one end of the rubber barrel. The rubber barrel is slidably connected to the connecting pipe. The end fixing member is connected to the other end of the connecting pipe and abuts against the other end of the rubber barrel.

[0011] In a further aspect, a limiting inclined groove is provided in the middle of the upper cone, and the limiting inclined groove is elastically connected to the elastic locking member for limiting the upper cone on the step at one end of the connecting pipe.

[0012] In a further aspect, the slip assembly includes an intermediate connecting ring and a plurality of slips provided at both ends of the intermediate connecting ring.

[0013] In a further aspect, a plurality of sliding grooves are provided on the conical surfaces of the upper cone and the lower cone near the slip assembly. One end of each of the plurality of slips away from the intermediate connecting ring is a conical surface and is respectively slidably connected to the sliding grooves through the conical surfaces.

[0014] In a further embodiment, slip teeth are provided on the upper surfaces of the plurality of slips, and the outer diameter of the intermediate connecting ring is smaller than the outer diameter of the upper surface of the slips.

[0015] In a further embodiment, the plurality of slip teeth are all in the shape of inclined saw teeth.

[0016] In a further embodiment, the inclination directions of the inclined saw-tooth slip teeth on the slips at both ends of the slip assembly are both towards the middle of the slip assembly.

[0017] In a further embodiment, the slips are made of high-frequency quenched ductile iron.

[0018] In a further embodiment, an opening groove is provided at one end of the connecting pipe extending from the adapter head, and a pin groove is provided at one end of the connecting pipe. A shear pin can be inserted into the pin groove and is slidably connected to the opening groove through the shear pin.

[0019] In a further embodiment, the elastic locking member includes a lock spring.

[0020] In a further embodiment, the shaft end fixing member includes a nut.

[0021] The present invention has the following beneficial effects:

[0022] By providing a connecting pipe, an upper cone, a slip assembly, a lower cone, a rubber barrel and a shaft end fixing member, the drillable bridge plug realizes simple on-site setting and releasing operations, and convenient and reliable construction.

[0023] The slip assembly is designed in front of the rubber barrel. After drilling out the slip assembly part, the bridge plug can be released. The drilling time is short (1-2 hours), the drilling distance is short at 125 mm, and the one-time success rate of use is high.

[0024] Adopting a double-end slip structure, and there are multiple tiles on each slip with opposite tooth directions, realizing two-way locking of the bridge plug, thereby ensuring the setting and sealing effects, enabling the bridge plug to withstand large upper and lower pressure differences, and the indoor and on-site tests verify that it reaches 70 MPa.

[0025] The drillable bridge plug is made of an easily drillable and grindable material by setting the slips. Even if the bridge plug does not fall off during release, it is very easy to drill and damage the slips through a fishing tool to relieve the extrusion of the slips on the rubber barrel, so that the bridge plug can be pulled out of the wellbore by the fishing tool without causing downhole major repair accidents, etc. It is particularly suitable for wellbore string process measures such as plugging bottom water, selective layer acid fracturing and backflow well testing in oil and gas well exploration and development. Description of the Drawings

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 Schematic diagram of a drillable and retrievable mechanical bridge plug in this embodiment;

[0028] In the figure: 1. Connecting pipe; 11. Pin slot; 2. Upper cone; 21. Docking head; 211. Opening slot; 22. Limiting inclined slot; 3. Elastic locking member; 4. Slip bushing assembly; 41. Intermediate connecting ring; 42. Slip bushing; 421. Slip bushing teeth; 5. Lower cone; 6. Rubber barrel; 7. Shaft end fixing member; 8. Slide groove. Specific embodiments

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0030] The present disclosure provides a drillable and retrievable mechanical bridge plug, including a connecting pipe 1, an upper cone 2, an elastic locking member 3, a slip bushing assembly 4, a lower cone 5, a rubber barrel 6 and a shaft end fixing member 7. The upper cone 2 is slidably connected to one end of the connecting pipe 1, and a docking head 21 is provided at one end of the upper cone 2, and the docking head 21 extends outside the connecting pipe 1. A limiting inclined slot 22 is provided in the middle of the upper cone 2, and the limiting inclined slot 22 is elastically connected to the elastic locking member 3 for limiting the upper cone 2 on the step at one end of the connecting pipe 1. The other end of the upper cone 2 is connected to one end of the slip bushing assembly 4. The slip bushing assembly 4 is slidably connected to the connecting pipe 1, and the other end is connected to one end of the lower cone 5. The lower cone 5 is slidably connected to the connecting pipe 1, and the other end of the lower cone 5 abuts against one end of the rubber barrel 6. The rubber barrel 6 is slidably connected to the connecting pipe 1. The shaft end fixing member 7 is connected to the other end of the connecting pipe 1 and abuts against the other end of the rubber barrel 6.

[0031] Its working principle or implementation method is that the drillable bridge plug is transported to the predetermined position of the wellbore as a whole by connecting the connecting pipe 1 with the central oil pipe. The inside and outside of the oil pipe are isolated. The wellhead is pressurized to push the upper cone 2 downward, so that the slip 42 presses and expands the embedded casing, and the rubber expands and separates the oil layer. When it moves to the position of the elastic locking member 3, the bridge plug will be released from the shear nail, and the shear nail will break, causing the bridge plug to detach. The bridge plug needs to be unsealed by unsealing the slip 42 and the rubber. During the unsealing operation, a grinding shoe with an inner fishing anchor is lowered. The outer diameter of the grinding shoe is smaller than the inner diameter of the casing, and the inner diameter is larger than the outer diameter of the packer. The outer diameter of the inner fishing anchor is smaller than the inner diameter of the tool. It is sleeved on the slip assembly 4 on the bridge plug. The slip 42 and the slip assembly 4 are removed by milling and drilling, and the slip assembly 4 is unsealed. At the same time, the fishing tool is introduced into the inner cavity of the bridge plug, the central pipe is lifted, the rubber is recovered, the packer is unsealed, and it is directly lifted out of the well.

[0032] The bridge plug realizes simple on-site sealing and unsealing operations, convenient and reliable construction, and can withstand large upper and lower pressure differences, up to 70MPa, and has a high success rate of one-time use. However, due to the complex environment underground, when the bridge plug needs to be removed later, it is often corroded and rusted, cannot be retrieved, or cannot be processed after being stuck. It is necessary to drill and grind the bridge plug, and the slip assembly 4 of the bridge plug is set to be made of easy-to-drill and grind material. Even if the bridge plug cannot be unsealed, it is easy to drill the slip assembly 4 through the drilling and fishing tools to release the squeezing of the rubber barrel 6, so that the bridge plug can be pulled out of the wellbore by the drilling and fishing tools, and no underground overhaul accidents will occur.

[0033] According to the above working principle, some preferred implementation structures or embodiments are provided, wherein the slip assembly 4 comprises an intermediate connecting ring 41 and a plurality of slips 42 arranged at both ends of the intermediate connecting ring 41. 6-9 slips 42 can be arranged at each end, preferably 8 slips 42, which are evenly distributed around the circumference, so as to improve the uniform force when the bridge plug contacts the well wall during setting, improve the setting strength of the slip assembly 4, and prevent the slip 42 from deviating, resulting in insufficient drilling and grinding of the drilling and fishing tool, and large particle size of the debris produced during drilling and grinding, which damages the drilling and fishing tool.

[0034] The upper cone 2 and the lower cone 5 are provided with a plurality of slide grooves 8 on the conical surface at one end close to the slip assembly 4, and the ends of the plurality of slips 42 away from the middle connecting ring 41 are provided with conical surfaces, and are slidably connected to the slide grooves 8 through the conical surfaces, respectively. This facilitates the sliding of the slips 42.

[0035] The upper surfaces of the plurality of slips 42 are all provided with slip teeth 421, and the outer diameter of the middle connecting ring 41 is smaller than the outer diameter of the upper surface of the slip 42. This facilitates the slips 42 at both ends to slide upward in the chute 8, so that the slip teeth 421 are in contact with the wellbore wall first.

[0036] The plurality of slip teeth 421 are all in an oblique sawtooth shape, which can improve the gripping force and the setting stability.

[0037] The inclined directions of the inclined serrated slips teeth 421 on the slips 42 at both ends of the slips assembly 4 are both towards the middle of the slips assembly 4. When setting the packer, it is further realized that it is not easy to slide on the wellbore wall.

[0038] The slips 42 are made of high-frequency quenched ductile iron. In this way, the hardness of the slips 42 is moderate and it is easy to machine.

[0039] One end of the connecting pipe 1 extending from the docking head 21 is provided with an opening groove 211, and one end of the connecting pipe 1 is provided with a pin slot 11. The pin slot 11 is inserted with a shear pin, and is slidably connected to the opening groove 211 through the shear pin. The easy release is realized through the shear pin.

[0040] The elastic locking member 3 includes a lock spring. In some embodiments, compared with the existing bridge plug where the slips 42 are arranged on both sides of the rubber barrel 6, the slips assembly 4 of this embodiment is arranged at the front end of the rubber barrel 6. The fishing tool does not need to drill and damage the rubber barrel 6, and the working efficiency of the drilling and milling process is improved without reducing the performance of the bridge plug in terms of bidirectional pressure and tension resistance.

[0041] In the embodiments of the present disclosure, the shapes and sizes of all the slips teeth 421 are the same and are all serrated. By adopting the structure where the rake angle and the clearance angle of the slips teeth 421 are the same, the barbed slips teeth 421 are prevented from getting stuck on the inner wall of the casing when the bridge plug is lifted or lowered. Especially in horizontal wells, the slips teeth 421 with the same rake angle and clearance angle can maximize the decomposition of the resistance of the uneven inner wall of the casing to the slips teeth 421 when the bridge plug is lifted or lowered, reduce the operation difficulty and the operating difficulty, and improve the success rate of setting and unsealing the bridge plug. At the same time, the sharp angle of the original slips teeth 421 is set into a tooth tip with a certain width, which reduces the damage to the casing and itself while ensuring that the slips teeth 421 firmly grip the casing, and improves the service life of the bridge plug itself.

[0042] The material of the slips teeth 421 is not limited by the material of the slips 42 pieces, which can make the anchoring effect of the slips 42 reach or exceed the anchoring effect of the integral slips 42, and reduces the drilling and milling volume compared with the integral slips 42. When the fishing tool drills and mills to the assembly groove, the slips teeth 421 will fall off, and the fishing tool does not need to drill and mill the slips teeth 421, making the slips 42 with the assembly groove easier to drill out compared with the integral slips 42. In other embodiments of the present disclosure, the slips teeth 421 have a falling-off structure in the vertical direction. When the fishing tool drills and mills, the slips teeth 421 are subjected to a force in the vertical direction and will fall off, further reducing the drilling and milling volume of the fishing tool. When the slips teeth 421 are subjected to a force in the horizontal direction, since the slips teeth 421 are in contact with the slips 42, they can withstand a large pressure.

[0043] When the slips 42 are damaged by the fishing tool, the extrusion of the slip assembly 4 on the rubber barrel 6 is released, so that the bridge plug can be pulled out of the wellbore by the fishing tool.

[0044] It should be noted that in this application, the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", etc. is based on the orientation or positional relationship shown in the drawings.

[0045] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0046] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and the above embodiments and the description in the specification only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A drillable mechanical bridge plug, It is characterized in that The invention comprises a connecting pipe (1), an upper cone (2), an elastic locking member (3), a slip assembly (4), a lower cone (5), a rubber barrel (6) and an axis end fixing member (7), wherein the upper cone (2) is slidably connected to one end of the connecting pipe (1), and a docking joint (21) is provided at one end of the upper cone (2), and the docking joint (21) extends out of the connecting pipe (1), and the elastic locking member (3) is connected to the connecting pipe (1) and is used to limit the position of the upper cone (2), and the upper cone (2) The other end of the axial end fixing member (7) is connected to one end of the slip assembly (4), the slip assembly (4) is slidably connected to the connecting pipe (1), the other end of the axial end fixing member (7) is connected to one end of the lower cone (5), and the lower cone (5) is slidably connected to the connecting pipe (1), the other end of the lower cone (5) is abutted against one end of the rubber barrel (6), the rubber barrel (6) is slidably connected to the connecting pipe (1), and the axial end fixing member (7) is connected to the other end of the connecting pipe (1) and abutted against the other end of the rubber barrel (6).

2. A drillable mechanical bridge plug according to claim 1, It is characterized in that The slip assembly (4) comprises a middle connecting ring (41) and a plurality of slips (42) arranged at both ends of the middle connecting ring (41).

3. A drillable mechanical bridge plug according to claim 2, It is characterized in that A plurality of slide grooves (8) are arranged on the conical surfaces of one end of the upper cone (2) and the lower cone (5) close to the slip assembly (4); the ends of the plurality of slips (42) away from the middle connecting ring (41) are arranged as conical surfaces, and are slidably connected to the slide grooves (8) respectively through the conical surfaces.

4. A drillable mechanical bridge plug according to claim 2, It is characterized in that The upper surfaces of the plurality of slips (42) are all provided with slip teeth (421), and the outer diameter of the intermediate connecting ring (41) is smaller than the outer diameter of the upper surface of the slips (42).

5. A drillable mechanical bridge plug according to claim 4, It is characterized in that The plurality of slip teeth (421) are all in an oblique sawtooth shape.

6. A drillable mechanical bridge plug according to claim 5, It is characterized in that The inclined directions of the oblique sawtooth-shaped slip teeth (421) on the slips (42) at both ends of the slip assembly (4) are both toward the middle of the slip assembly (4).

7. The drillable mechanical bridge plug according to claim 2, It is characterized in that The slip (42) is made of high-frequency quenched ductile iron.

8. The drillable mechanical bridge plug according to claim 1, It is characterized in that A limiting inclined groove (22) is provided in the middle of the upper cone (2), and the limiting inclined groove (22) is elastically connected to the elastic locking member (3) and is used to limit the upper cone (2) on the step at one end of the connecting pipe (1).

9. The drillable mechanical bridge plug according to claim 1, It is characterized in that An end of the butt joint (21) extending from the connecting pipe (1) is provided with an open groove (211), and one end of the connecting pipe (1) is provided with a pin groove (11), a shearable pin is inserted into the pin groove (11), and the shearable pin is slidably connected to the open groove (211).

10. The drillable mechanical bridge plug according to claim 1, It is characterized in that The elastic locking member (3) comprises a locking spring, and the shaft end fixing member (7) comprises a nut.

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